This trophy requires you to find all Gummi Ship blueprints in the game (Though on PS4 you'll only need to find 30). Finding all blueprints require you to do certain things like collect blueprints dropped by enemy ships on gummi ship routes, do level 3 gummi ship missions for all of the worlds, and defeating up to 5,000 Heartless in the game.
Here are some helpful resources for gummi ship blueprints:
For details on all of the gummi ship blueprints, take a look at the full list of all Gummi Ship Blueprints from the Kingdom Hearts Wikia, The Keyhole.
For really good tips on how to do all of the Gummi Ship missions, take a look at this GameFAQs Gummi Ship Mission Guide by GameFAQs user Primum Mobile.
The gummi ship is probably the most hated thing in the game for most people, however the missions truly aren't so bad and you'll likely find that out when starting to play them. It is all a matter of learning how to build your ship and knowing what to put on your ship for each mission. Take each mission one-by-one by playing the easy ones first and don't get frustrated. Thankfully, most of the missions are pretty fairly easy, but the hardest missions are the level 3 mission for Neverland, Atlantica, and Traverse Town along with missions 1 and 2 being hard for The End of the World. It's recommended you save those for close to last for when you have experience with the gummi ship.
Highly Advised (Regarding Placement of Monstro): After sealing the keyhole in Agrabah and taking a flight to the next world for the first time, set a course for Halloween Town (the planet to the northeast of Agrabah). Atlantica is arguably one of the hardest mission routes and you'll have to take the route several times and the last thing you need is a giant whale getting in the way of your route and intercepting you half the time (it doesn't always intercept you, but the chances of it probably aren't wanted). So again, set off for Halloween Town instead of Atlantica after sealing Agrabah's keyhole and leaving that world for the first time.